National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KDTX 090956
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
556 AM EDT Sun May 9 2021


.AVIATION...

A warm front remains draped across southern Indiana and Ohio with
the surface low now over Missouri. this low will track along the
front today with the northern edge of the precipitation shield
(already present on radar along the state line) inches northward.
Model trend has been to restrict the northern extent of the rain
this afternoon, keeping the bulk of the activity south of PTK. Will
drop the Detroit tafs to MVFR with heaviest rain showers this
afternoon for a few hours and leave PTK with a tempo for now as they
are still in question with the shift south. MBS and FNT will most
likely stay dry with only elevated VFR CIGS and backing winds to
account for. Rain should come to an end late this afternoon with dry
conditions the rest of the night while winds turn from northeast to
northwest.

For DTW... Edge of the rain is just south of the state line as of
10Z and will continue to slowly inch northward this morning. Rain
will most likely hold off til around 14Z, peaking in intensity
around 16-20Z before the back edge exits east by 00Z. Winds will
flip around to the northwest this evening with clouds largely
scattering out.

.DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 feet or less mid morning into late
  afternoon.

&&

.PREV DISCUSSION...
Issued at 315 AM EDT Sun May 9 2021

DISCUSSION...

A convective complex (MCS) will continue to advance across Missouri
in the pre dawn hours this morning. A region of showers and
stratiform rain extends east/northeast from this feature across the
northern and central Ohio Valley. This eastward extension of precip
is within a tight mid level baroclinic zone. Ascent tied to the
entrance region of a 130-140kt upper jet across the northern/eastern
Great Lakes is aiding in the frontogenetical forcing along the mid
tropospheric front. Observational trends overnight raise some
concerns that adds a little bit more uncertainty to rain chances for
Se Mi today. First off, the upscale growth to the convection across
Missouri has led to a mid level MCV which looks to track farther
south across the Ohio Valley compared to what most model solutions
suggest. The other item of concern is that there appears to be more
contraction within the mid level front which has actually caused a
little drying trend on the northern edge of the rain shield.

During the course of the morning and early afternoon there is still
expected to be a northward shift in the entrance region jet dynamics
which will support a better push of system relative moist isentropic
ascent farther up the elevated portion of the mid level front and
into portions of southern Mi. This will result in a northward shift
to the rain as the mid level wave advances across the Ohio Valley.
In light of the above mentioned factors, there will be a reduction
in the chances of rain to likely/chance across the northern Detroit
suburbs to low chance across the I 69 corridor and removal of pops
farther north. Categorical pops will be retained along/south of an
Ann Arbor/Detroit line, although forecast rainfall amounts will be
cut back as the more robust mid level fgen response looks to be
setting up south of the state line. Given the expectation for ample
clouds and at least some light rain, forecast highs only in the 40s
across metro Detroit/Ann Arbor and points south look reasonable. The
prospects for a little more insolation potential will support
forecast highs in the mid/upper 50s across the northern half of the
forecast area.

The eastward departure of the Ohio Valley wave will support a
drying/clearing trend tonight. The cold resident airmass will drop
nighttime temps down into the 30s tonight. Long wave troughing
extending from the Great Lakes into ern Canada will sustain this
cold airmass overhead Monday and Tuesday, leading to a continuation
of well below normal temperatures. A mid level trough axis is
forecast to traverse Se Mi Tuesday from north to south. Despite
limited moisture, steep mid level lapse rates courtesy of 500mb
temps forecast to drop to -32C and ascent occuring within the peak
in the diurnal cycle should support at least some scattered
afternoon showers on Tuesday. Rising mid level heights toward the
latter half of the week will support a late week warming trend,
allowing temps to return toward mid May averages.

MARINE...

High pressure will shift slightly north as low pressure tracks
eastward from the central Plains towards the northern Ohio Valley
late tonight into Sunday, bringing widespread rainfall to the
southern half of the local waters. Light and variable winds will
reorient northeasterly in response to the low pressure system and
become moderate in strength, especially across western Lake Erie,
where the tightest pressure gradient will help yield gusts around 25
knots during the day Sunday and building wave heights of 3-5 feet
posing hazardous small craft conditions. Winds will back more
northwesterly and become more moderate in strength across all waters
for early next week as high pressure becomes reestablished across
the Great Lakes.

HYDROLOGY...

There has been a southward shift in the frontal system to affect
southern Michigan today. This will keep the higher rainfall totals
south of the state. A half to three quarters of an inch of rain is
possible along the Ohio border. In light of recent trends, total
forecast rainfall amounts have been scaled back to a quarter inch
along the I-94 corridor, tapering to little or now rain up to the I-
69 corridor.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...Small Craft Advisory from 10 AM this morning to 10 PM EDT this
     evening for LEZ444.

&&

$$

AVIATION.....DRK
DISCUSSION...SC
MARINE.......IRL
HYDROLOGY....SC


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.